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An investigation of plasma and salivary oxytocin responses in breast- and formula-feeding mothers of infants


  • This study was funded by NIH grants K01DA099949, R01HL084222, and RR00046. Special thanks are given to Cheryl Walker and Chihiro Christmas for their expertise with plasma and saliva sample processing, and to Mala Elam, RN, Marisa DeBurkarte, Jay Gregg, Patty Kuo, Riti Shah, Noah Pagano, Nick Zerona, Nitisha Desai, Michael Addamo, Janna Williams, and Poorvi Oza for their valuable contributions to data collection, management and analysis.

Address reprint requests to: Karen M. Grewen, Ph.D., University of North Carolina at Chapel Hill, CB#: 7175, Medical School Wing D, Chapel Hill, NC 27599-7175. E-mail:


Oxytocin (OT) is a peptide increasingly studied in relation to human social interactions, affiliation, and clinical disorders. Studies are constrained by use of invasive blood draws and would benefit from a reliable salivary OT assay. Our goals were to examine feasibility of salivary OT measurement, compare salivary to plasma OT responses in 12 breast- and 8 formula-feeding mothers, and assess the degree of correlation between plasma and salivary OT. Using a commercial EIA kit, we measured OT in 5 saliva and 7 plasma samples in a protocol designed to elicit changes in OT (Rest, Infant Interaction, Stress, Feeding). Breast-feeders had higher OT levels than formula-feeders across all conditions in plasma (+36%) and saliva (+23%). OT levels and ranges were similar in saliva and plasma, with slightly greater variance in saliva. Concurrently sampled plasma and salivary OT were correlated at end of Baseline Rest (r=+.59, p=.022) and Post-Stress Recovery (r=+.59, p=.025). These data suggest that salivary OT assay is feasible, and will be of value where plasma samples are not possible. Validation with larger samples is needed.